This invention relates to a flanged bearing adapted to support a shaft and to be fitted in an opening in a housing, and to a process for making the same.
Prior art flanged bearings have been known which comprise a cylindrical body and a flange that extends radially outwardly at one end of the cylindrical body, the cylindrical body being designed to support loads applied transversely and the flange to support loads applied axially.
In the flanged bearings that are conventionally employed in the wheels provided on the undersurfaces of machines used in civil engineering such as bulldozers and power shovels, the frictionally slidable portions of the bearings are subjected to high loads and, thus, these frictionally slidable portions are formed of steels having high mechanical strength with load-resistant alloys such as LBC and/or PBC applied thereto. Thus, the portions of the bearings that fit tightly in an opening in a housing exhibit very high strength.
FIGS. 9 and 10 show a prior art flanged bearing adapted to support a shaft and to be fitted in an opening in a housing. The prior art flanged bearing is generally shown by reference numeral 20 and comprises a cylindrical body 21 and a radially outwardly extending flange 22 at one end of the cylindrical body 21. Small chamfers 24, 24 are provided at the opposite ends of the inner periphery of the cylindrical body 21; and wherein the length of the clearance means is greater or equal to the thickness of the flange plus the depth of the housing chamfer. The provision of the chamfers 24, 24 facilitates the receiving of a shaft 15 in the bearing and protects the acutely angled ends of the cylindrical body against the possibility of breakage when the shaft vibrates or bends during rotation.
However, after continuous use of the flanged bearing over a long period of time, a crack or cracks K tend to develop in the cylindrical body 21 at the end thereof adjacent to the flange 22, as shown in FIG. 10.
After extensive studies of the cause of such cracking in the prior art flanged bearing. The inventor has found that the chamfers formed at the opening in the housing have an influence. These chamfers at the housing opening allow the flanged bearing to fit smoothly in the housing. That is, the clearance between the outer periphery of the housing body and the outer diameter of the cylindrical body of the flanged bearing is usually small, on the order of 0.05-0.2 mm, and if the entrance to the housing opening remains rough as initially formed, this entrance presents an acutely angled edge and the outer periphery of the cylindrical body of the flanged bearing is thus caught by the acute edge of the housing opening to such an extent that the flanged bearing cannot be fitted into the housing opening. For this reason, the entrance to the housing opening is formed with a chamfer to allow the flanged bearing to fit into the housing opening easily.
Furthermore, when an excessively high load is applied to the shaft 15 received in the bearing and/or the bearing and shaft are eccentric to each other, the shaft 15 tends to bend as shown in FIG. 10 while rotating. At this time, a substantial portion of the load is applied to a portion of the cylindrical body, that is, the end of the cylindrical body adjacent to the flange 22, but since the chamfer 24 is formed adjacent to the entrance of the opening 17 in the housing 18 where the non-flanged end of the cylindrical body is positioned, a cavity is left into which the non-flanged end of the cylindrical portion or body bends. Thus, as the shaft bends cylindrically, the end tends to bend into and out of the cavity and metallic fatigue therefore occurs at that end which may lead to development of cracking of the material of the cylindrical body.